Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds value beyond them by stating "Datos públicos. Sin clave." (public data, no API key needed) and by enumerating the kind of output returned (confianza, motivo, periodicidad, plazo) — genuine auth and payload context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short fragments with no filler, and the core purpose is front-loaded. The parenthetical list of output fields sits a bit awkwardly for a description of an input-driven tool, but nothing is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple two-parameter read-only public tool this covers purpose, output shape and auth adequately, and no output schema exists to carry the return contract. The gaps are the undocumented code_type parameter and the missing distinction from sibling lookup tools, leaving it minimum-viable rather than complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must carry the burden and largely does not. It only alludes to "un código" as input and never explains the code_type enum (iae vs cnae), the default, or the numeric/dot pattern constraint. An agent cannot tell from the description what code family it should pass.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a concrete resource and behavior: returning the AEAT tax forms ("Modelos AEAT") applicable to a given code. An agent can distinguish it from pure lookups like buscar_codigo or detalle_iae in intent. It stops short of explicitly contrasting itself with those siblings, so it is clear but not fully differentiated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no when-to-use guidance and no mention of alternatives, despite a crowded sibling set (detalle_iae, detalle_cnae, buscar_codigo, calendario_fiscal). The agent gets a purpose but no routing rule for choosing this tool over the near-neighbors.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.